In recent years, a touch-operating input device utilizing display means such as a liquid crystal display panel has been in practical use as an operation input portion of an electronic device. In the touch-operating input device, button input operation is performed by performing touch operation on an operation button displayed on a screen of a touch panel. Detection of whether the operation button is touched and operated is performed by a function of a touch sensor that is provided to correspond to the operation button. In this respect, there is provided a touch-operating input device configured to display by illuminating an operation button that can be operated from among a plurality of operation buttons such that an operator can easily find the operation button that can be operated such those disclosed in paragraph [0037] of Japanese Patent Application Laid-Open No. 2006-146701, for example.
However, merely displaying the operation button that can be operated sometimes makes it difficult to find an operation button that cannot be operated at this moment but is to be operated subsequently. For example, a case in which an in-vehicle air conditioner, audiovisual device, and car navigation device are operated by touching a button on an identical touch-input device, is taken as an example. In the case where only an operation button that can be operated is displayed, if the audiovisual device is operated after operation of the air conditioner, the operation button of the audiovisual device, which is not displayed, may not be immediately found because it is not to be operated. This happens because the operation button for the audiovisual device is either not displayed or displayed but is in a state difficult to find even though the operation button for the air conditioner is displayed.
To make it easy to find an operation button that is either not displayed or displayed but is in a state difficult to find, it is preferable to illuminate and display, at the same time if possible, such an operation button that will be probably operated. However, if such an operation button is also illuminated and displayed at the same time, it may be difficult to find which one of the operation buttons the operator has operated or which one of the operation buttons is the one that can be operated. To state it differently, such an arrangement may cause poor operability of the touch-operating input device.